Technical Field
The present invention relates to a method in analytical chemistry. More specifically, the present invention relates a method for detecting and determining the concentration of one or more haloether compounds in an aqueous sample by solid phase microextraction and gas chromatography-mass spectrometry techniques.
Description of the Related Art
The “background” description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description which may not otherwise qualify as prior art at the time of filing, are neither expressly or impliedly admitted as prior art against the present invention.
Haloethers are compounds which contain an ether moiety (R—O—R) and halogen atoms attached to the aryl or alkyl groups. Haloethers are a class of disinfection by-products (DBPs) that are unintentionally produced from the reactions of disinfectants with organic matter naturally present in the water [Richardson, S. D., 2009. Water Analysis: Emerging Contaminants and Current Issues. Analytical Chemistry, 81, 4645—incorporated herein by reference in its entirety]. They are harmful to humans and have been shown to be carcinogenic even at low parts per billion (ppb) levels. In addition to that haloethers are widely used in industry as solvents for fiber processing, polymers, pesticides, medicine, and ion exchange resins and thereby enter into the aqueous environment [Chiing. C. C., Ren. J. W., Chun, Y., Chung. S. L., 2009. Bis (2-chloroethoxy) methane degradation by TiO2 photocatalysis: parameter and reaction pathway investigations. J. Hazard. Mater 172, 1021; Jing. S. C., Shang. D. H., 2007. Determination of haloethers in water with dynamic hollow fiber liquid-phase microextraction using GC-FID and GC-ECD. Talanta 71, 882; Montgomery and Welkom 1990. Montgomery, J. H., Welkom, L. M., 1990. Groundwater Chemical Desk Reference, Lewis Publishers, Chelsea, Mich.; Thomas, O. V., Stork, J. R., Lammert, S. L., 1980. The chromatographic and GC/MS analysis of organic priority pollutants in water. J. Chromatogr. Sci. 18, 58—each incorporated herein by reference in its entirety]. Haloethers are persistent contaminants and are of great concern because of their carcinogenicity and toxicity [Sittig, M., 1991. Handbook of Toxic and Hazardous Chemicals and Carcinogens, third ed., Noyes Public, New Jersey; Shang, D. H., Yi, T. C., Cheng. S. L., 1997. Determination of haloethers in water by solid-phase microextraction. J. Chromatogr. A 769, 239; Fawell, J. K., Hunt, S., 1988. Environmental Toxicology: Organic Pollutants, Wiley, New York, (Chapter 9); Wennrich, L., Engewald, W., Poppb, P., 1997. Determination of chloroethers in aqueous samples using solid-phase microextraction. Acta Hydrochim. Hydrobiol. 25, 329—each incorporated herein by reference in its entirety].
In 1979, the United States Environmental Protection Agency (USEPA) classified five Haloethers as priority pollutants, and proposed a maximum allowed contaminant level (MCL) of 500 μg/L [USEPA 1980. United States Environmental Protection Agency, Office of Water Regulations and Standards Criteria and Standards Division Washington D.C. 20460 440/5-80-050 October 1980—incorporated herein by reference in its entirety]. 4-chlorophenyl phenyl ether (CPPE) and 4-bromophenyl phenyl ether (BPPE) are among these priority haloethers, and their chemical structures are shown in FIGS. 1A and 1B. The physical properties of CPPE and BPPE are listed in Table 1.
TABLE 1Physical properties of CPPE and BPPE.Physical propertiesCPPEBPPEMolecular weight (g mol−1)204.6249.1Solubility at 20-25° C. (mg L−1)1.430.82Boiling point (° C.)161305Vapor pressure at 20-25° C. (mmHg)0.00160.0005Henry's law constant at 20° C.0.0120.009Diffusion coefficient in air (cm2 s−1)0.0480.047Diffusion coefficient in water (cm2 s−1)6.18E−066.27E−06
USEPA methods 611 and 625 that are based on liquid-liquid extraction (LLE) were established to determine haloethers from aqueous samples [Thomas, O. V., Stork, J. R., Lammert, S. L., 1980. The chromatographic and GC/MS analysis of organic priority pollutants in water. J. Chromatogr. Sci. 18, 583; Shang, D. H., Yi, T. C., Cheng. S. L., 1997. Determination of haloethers in water by solid-phase microextraction. J. Chromatogr. A 769, 239—each incorporated herein by reference in its entirety]. However, these techniques require hazardous solvents, multi-step and time-consuming extraction procedures, and the risk of haloether loss in extraction and concentration steps [Wennrich, L., Engewald, W., Poppb, P., 1997. Determination of chloroethers in aqueous samples using solid-phase microextraction. Acta Hydrochim. Hydrobiol. 25, 329—incorporated herein by reference in its entirety]. As a result, poor precision and low recoveries were reported [USEPA 1980. United States Environmental Protection Agency, Office of Water Regulations and Standards Criteria and Standards Division Washington D.C. 20460 440/5-80-050 October 1980—incorporated herein by reference in its entirety].
Over the years, different analytical methods have been developed for the determination of haloethers, such as, liquid phase microextraction (LPME), hollow fiber LPME (HF-LPME) and single drop microextraction (SDME) (Zheo et al., 2002), Solid-phase microextraction (SPME) [He, Y., Lee, H. K., 1997. Liquid-Phase Microextraction in a Single Drop of Organic Solvent by Using a Conventional Microsyringe. Anal. Chem. 69, 46; Wang, Y., Kwok, Y. C., He, Y., Lee, H. K., 1998. Application of dynamic liquid-phase microextraction to the analysis of chlorobenzenes in water by using a conventional microsyringe. Anal. Chem. 70, 461; Chiang, S., Huang, D., 2007. Determination of haloethers in water with dynamic hollow fiber liquid-phase microextraction using GC-FID and GC-ECD. Talanta 71, 882-886; Shen, G., Lee, H. K., 2002. Hollow fiber-protected liquid-phase microextraction of triazine herbicides. Anal. Chem. 74, 64; —each incorporated herein by reference in its entirety]. Among these methods, SPME is a solvent-free microextraction technique which combines sampling, sample clean-up and pre-concentration into a single step [Ouyang, G., Vuckovic, D., Pawliszyn, J., 2011. Nondestructive Sampling of Living Systems Using in Vivo Solid-Phase Microextraction. Chem. Rev., 111, 2784; Zeng, J. B., Zou, J., Song, X. H., Chen, J. M., Ji, J. J., Wang, B., Wang, Y. R., Ha, J. H., Chen, X., 2011. A new strategy for basic drug extraction in aqueous medium using electrochemically enhanced solid-phase microextraction. J. Chromatogr. A 1218, 191—each incorporated herein by reference in its entirety].
Although SPME typically involves a relatively straightforward, single-step extraction procedure, SPME fiber capacity is low and not suitable for large volume samples. In light of this deficiency, as well as the shortcomings of other methods as set forth above, the present disclosure provides a simple and safe method for determining the concentration of haloether compounds in an aqueous sample that exhibits excellent analyte recovery at both low and high background matrices.